Often imports can be a dodgy way of purchasing a used car, make sure the registration details are above board and definately make sure It's in some way legal where you live lol. Also, I'm not sure about Aus (I'm guessing AUD means Aus dollars?) but in the UK most if not all Jap imports have genuine tags on each of the front seatbelts (if they are the factory fitted ones!) that states the exact year of manufacture, just compare this with the details you have of the car (although It's still not garenteed though, obviously).

As for your second question, a Stock R34 is quite a bit newer so It will probably be a wiser option for the money although on the other hand the R33 Isn't a lot older than the R34 so It's bound to be just as reliable (aint they all...they're Nissans!) and if It's slightly modded even better, although make sure it is fast and doesn't just look it lol! Also look for a faily low milage example as these will be easier to sell on afterwards, It would also help you to remember that a non-import (or at least an Aus spec version) is always going to be safer...although probably too expensive lol, infact I dont even think R34 Skylines are available in anything other than Jap spec lol

whats up im obsessed with car and if there is any thing i know about its skylines. first the best choice is an r34 than r33 than r32. the r34 is the most expecive but is the fastest it's usally 50k give or take a few. it also has the most avalible parts. the r33 is comperable to the r34 but its about 25-35k (your best bet). and the r32 is about 17-28k but isn't as good as the other 2. two good places to look are js-garage.com and motorex.net. good luck i hope you can get the skyline